侧边栏如何展开与收起

1.效果图：


2.实现思路：
利用el-menu的isCollapse来实现。

  <div class="left" 
  :style="{width:isCollapse?'60px':'200px'}"
  >
  <el-menu default-active="1-4-1" class="el-menu-vertical-demo" :collapse="isCollapse">
    <el-submenu index="1">
      <template slot="title">
        <i class="el-icon-location"></i>
        <span slot="title">导航一</span>
      </template>
      <el-menu-item-group>
        <span slot="title">分组一</span>
        <el-menu-item index="1-1">选项1</el-menu-item>
        <el-menu-item index="1-2">选项2</el-menu-item>
      </el-menu-item-group>
      <el-menu-item-group title="分组2">
        <el-menu-item index="1-3">选项3</el-menu-item>
      </el-menu-item-group>
      <el-submenu index="1-4">
        <span slot="title">选项4</span>
        <el-menu-item index="1-4-1">选项1</el-menu-item>
      </el-submenu>
    </el-submenu>
    <el-menu-item index="2">
      <i class="el-icon-menu"></i>
      <span slot="title">导航二</span>
    </el-menu-item>
    <el-menu-item index="3" disabled>
      <i class="el-icon-document"></i>
      <span slot="title">导航三</span>
    </el-menu-item>
    <el-menu-item index="4">
      <i class="el-icon-setting"></i>
      <span slot="title">导航四</span>
    </el-menu-item>
    </el-menu>
    <i  class="switch" :class="isCollapse?'el-icon-s-unfold':'el-icon-s-fold'"   @click="isCollapse=!isCollapse"></i>
    </div>  
  </div>

// data中需定义isCollapse.
  .el-menu-vertical-demo:not(.el-menu--collapse) {
    
    
    width: 200px;
    min-height: 400px;
  }
  .left{
    
    
    position: relative;
    height: 600px;
  }
  .switch{
    
    
    display: inline-block;
    width: 40px;
    position: absolute;
    left: 10px;
    bottom: 10px;
  }